Self-aligned repairing process for barrier layer

ABSTRACT

A self-aligned repairing process for a barrier layer is provided. A repair layer is formed by chemical vapor deposition using an organometallic compound as a precursor gas. The precursor gas adsorbed on a dielectric layer exposed by defects in a barrier layer is transformed to an insulating metal oxide layer, and the precursor gas adsorbed on the barrier layer is transformed to a metal layer.

REFERENCE TO RELATED APPLICATION

The present application is a divisional application of U.S. applicationSer. No. 14/151,711, filed Jan. 9, 2014, which is hereby incorporated byreference in its entirety.

BACKGROUND

As the design rule for integrated circuits is continuously scaled down,the dimension of damascene opening is continuously reduced. Therefore,the step coverage of a barrier layer covering the inner surface of thedamascene opening is getting worse, and defects may be formed in thebarrier layer. For example, if 30-50 Å of barrier layer is blanketdeposited on a wafer, the thickness of the barrier layer on sidewalls ofopenings, including vias and trenches, may be less than 5-10 Å.Therefore, defects can be easily formed in the barrier layer located onsidewalls of openings.

Since barrier layer is used to surrounding the later formed metalinterconnect to prevent metal from diffusing into the dielectric layerwhere the damascene opening is located, these defects in the barrierlayer provide passages for the metal diffusion. Moreover, the low-kdielectric layer mostly made from porous dielectric materials make theproblem of metal diffusion through defects in the barrier layer moreserious, since the larger the total pore volume of the porous dielectricmaterial has, the lower the dielectric constant of the porous dielectricmaterial has.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a flowchart of a self-aligned repairing process for a barrierlayer according some embodiments of this disclosure.

FIGS. 2A-2G are cross-sectional diagrams showing a self-alignedrepairing process for a barrier layer according some embodiments of thisdisclosure.

The drawings, schematics and diagrams are illustrative and not intendedto be limiting, but are examples of embodiments of the disclosure, aresimplified for explanatory purposes, and are not drawn to scale.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

According to some embodiments, a self-aligned repairing process for abarrier layer is provided. A damascene opening is formed in a dielectriclayer on a substrate, and the surface of the dielectric layer has freehydroxyl groups. A barrier layer is then on the dielectric layer tocover inner surfaces of the damascene opening. A precursor layer isformed on the barrier layer by chemical vapor deposition using anorganometallic compound containing a central metal atom as a precursorgas, wherein the central metal atom can be Al, Ru, Co, Mn, or Ta, forexample. Finally, the precursor layer is transformed to a repair layer.The precursor layer on the dielectric layer exposed by defects in thebarrier layer is transformed to an insulating metal oxide layer, and theprecursor layer on the barrier layer is transformed to a metal layer.

According to some other embodiments, a method of forming a damascenestructure is provided. A damascene opening is formed in a dielectriclayer on a substrate, and the surface of the dielectric layer has freehydroxyl groups. A barrier layer is then on the dielectric layer tocover inner surfaces of the damascene opening. A repair layer isdeposited on the barrier layer by chemical vapor deposition using anorganometallic compound containing a central metal atom as a precursorgas. The central metal atom can be Al, Ru, Co, Mn, or Ta, for example.The precursor gas adsorbed on the dielectric layer exposed by defects inthe barrier layer is transformed to an insulating metal oxide layer, andthe precursor gas adsorbed on the barrier layer is transformed to ametal layer. Next, a seed layer is deposited on the repair layer. Ametal layer is formed on the seed layer to fill in the damasceneopening. An upper portion of the metal layer, the seed layer, the repairlayer, the barrier layer, and the dielectric layer is then removed toform a metal interconnect in the damascene opening.

According to some other embodiments, a damascene structure is alsoprovided. In the damascene structure, a dielectric layer is disposed ona substrate, wherein the dielectric layer has a damascene opening. Abarrier layer is disposed on inner surface of the damascene opening. Arepair layer is disposed on the barrier layer, wherein the repair layerdisposed on the barrier layer is composed of a metal, and the repairlayer disposed on the dielectric layer exposed by defects in the barrierlayer is composed of insulating metal oxide. A seed layer is disposed onthe repair layer. A metal interconnect is disposed in the damasceneopening.

FIG. 1 is a flowchart of a self-aligned repairing process for a barrierlayer according some embodiments of this disclosure. FIGS. 2A-2G arecross-sectional diagrams showing a self-aligned repairing process for abarrier layer according some embodiments of this disclosure. FIGS. 1 and2A-2G are referred below at the same time.

In step 110 of FIG. 1 and FIG. 2A, damascene openings 215 are formed ina dielectric layer 210 on a substrate 200. The dielectric layer 210 canbe made from a low-k dielectric material having some free hydroxyl (—OH)groups on the surface thereof. The low-k dielectric material is definedto be a dielectric material have a dielectric constant lower than thedielectric constant of silicon dioxide. Common low-k dielectric materialincludes fluorine-doped silicon dioxide, carbon-doped silicon dioxide,porous silicon dioxide, porous carbon-doped silicon dioxide, spin-onsilicone based polymeric dielectric (such as hydrogen silsesquioxane(HSQ) and methylsilsesquioxane (MSQ)). The method of forming thedamascene openings 215 can be photolithography and etching, for example.

In step 120 of FIG. 1 and FIG. 2B, a barrier layer 220 is formed on thedielectric layer 210 and on the inner surface of the damascene openings215. The barrier layer 220 on sidewalls of the damascene openings 215may have some defects 225. The material of the barrier layer 220 can bemetal or conductive ceramics. The metal above can be cobalt, ruthenium,tantalum, chromium, nickel, nichrome, hafnium, niobium, zirconium,vanadium, or tungsten, for example. The conductive ceramics above can betantalum nitride, indium oxide, copper silicide, tungsten nitride, ortitanium nitride, for example. The formation method of the barrier layer220 can be physical vapor deposition or chemical vapor deposition.

Next, a repair layer is formed on the barrier layer 220 by chemicalvapor deposition. The whole process of the formation of the repair layercan be divided into two stages. In the first stage (i.e. the step 130 ofFIG. 1 and FIG. 2C), a precursor gas is adsorbed on the surface of thebarrier layer 220 and the dielectric layer 210 exposed by defects 225 inthe barrier layer 220 to form a precursor layer 230. The precursor gasis an organometallic compound containing a central metal atom andsurrounding organic ligands.

In the second stage (i.e. the step 140 of FIG. 1 and FIG. 2D), theprecursor layer 230 is transformed to a repair layer 235 including ametal portion 235 a and an insulating metal oxide portion 235 b. Themetal portion 235 a is transformed from the precursor layer 230 adsorbedon the barrier layer 220. However, the insulating metal oxide portion235 b is transformed from the precursor layer 230 adsorbed on thedielectric layer 210 exposed by the defects 225 in the barrier layer220, since the surface of the dielectric layer 220 has some freehydroxyl groups, which can coordinate to the central metal atom of theprecursor gas. Therefore, the organometallic compound coordinated by thefree hydroxyl groups of the dielectric layer 210 is transformed toinsulating metal oxide.

The central metal atom above can be Al, Ru, Co, Mn, or Ta, for example.When the central metal atom is Al, the organometallic compound can betrimethylaluminum [Al(CH)₃], or triethylaluminum [Al(C₂H₅)₃], forexample.

When the central metal atom is Ru, the organometallic compound can betricarbonyl [(1,2,3,4-eta)-1,3,-cyclohexadiene] ruthenium, trirutheniumdodecacarbonyl [Ru₃(CO)₁₂], bis(ethylcyclopentadienyl) ruthenium[Ru(EtCp)₂], bis(methylcyclopentadienyl) ruthenium [Ru(MeCp)₂], ortris(acetylacetonate) ruthenium [Ru(acac)₃], for example.

When the central metal atom is Co, the organometallic compound can bedicarbonyl cyclopentadiene [CpCo(CO)₂], or dicobalt hexacarbonyltert-butylacetylene [CO₂(CO)₆[HC≡C—C(CH₃)₃], for example.

When the central metal atom is Mn, the organometallic compound can bedimanganese decacarbonyl [Mn₂(CO)₁₀].

When the central metal atom is Ta, the organometallic compound can bepentakis(dimethylamino) tantalum [Ta(NMe₂)₅], tris(dimethylamino)(tert-amylimido) tantalum [Ta=N-t-C₅H₁₁(NMe₂)₃], tris(ethylmethylami no)(tert-butylimido) tantalum [Ta=N-t-Bu(NMeEt)₃], or tris(diethylamino)(tert-butylimido) tantalum [Ta=N-t-Bu(NEt₂)₃], for example.

The chemical vapor deposition (CVD) above can be thermal CVD,plasma-enhanced CVD, metal-organic CVD, atomic layer deposition (ALD),thermal ALD, or plasma-enhanced ALD, for example.

In step 150 of FIG. 1 and FIG. 2E, a seed layer 240 for a later formedmetal layer is formed on the repair layer 235. The seed layer 240 can bemade from Cu, Co, Al, Ag, or any combinations thereof, for example. Theformation method of the seed layer 240 can be sputtering or evaporation.

In step 160 of FIG. 1 and FIG. 2F, a metal layer 250 is next formed onthe seed layer 240. The metal layer 250 can be made from copper, forexample. The formation method of the metal layer 250 can beelectroplating, for example.

Finally, in step 170 and FIG. 2G, a top portion of the metal layer 250,the seed layer 240, the repair layer 235, the barrier layer 220, and thedielectric layer 210 are removed to leave metal interconnects 250 a inthe damascene openings 215. The removal method can be chemicalmechanical polishing, for example.

Accordingly, a self-aligned repairing process for a barrier layer isprovided. The repair layer is formed by chemical vapor deposition. Anorganometallic compound is used as a precursor gas. The precursor gasadsorbed on the dielectric layer exposed by defects in the barrier layeris transformed to an insulating metal oxide layer, and the precursor gasadsorbed on the barrier layer is transformed to a metal layer.Therefore, the later-formed metal interconnects and the dielectric layercan be completely isolated by the barrier layer and the repair layer toprevent the metal of the metal interconnects from diffusing into thedielectric layer through defects in the barrier layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A damascene structure, comprising: a dielectriclayer disposed on a substrate and having a damascene opening; a barrierlayer disposed on the dielectric layer having the damascene opening, andcomprising two portions separated by a defect; a repair layercomprising: a conductive portion disposed on the two portions of thebarrier layer; and an insulating portion disposed in the defect; and aseed layer conformally disposed on the repair layer.
 2. The damascenestructure of claim 1, wherein the defect is on an inner surface of thedamascene opening and between the two portions of the barrier layer. 3.The damascene structure of claim 1, wherein the defect is exposing thedielectric layer.
 4. The damascene structure of claim 3, wherein theinsulating portion of the repair layer is covering the dielectric layerexposed by the defect.
 5. The damascene structure of claim 1, whereinthe conductive portion of the repair layer is composed of a metal. 6.The damascene structure of claim 5, wherein the metal is Al, Ru, Co, Mn,or Ta.
 7. The damascene structure of claim 1, wherein the insulatingportion of the repair portion is composed of an insulating metal oxide.8. The damascene structure of claim 1, wherein the dielectric layer ismade of a low-k dielectric material.
 9. The damascene structure of claim1, wherein the dielectric layer has a surface with a plurality of freehydroxyl (—OH) groups.
 10. The damascene structure of claim 1, whereinthe barrier layer is made of metal or conductive ceramic.
 11. Thedamascene structure of claim 10, wherein the metal is cobalt, ruthenium,tantalum, chromium, nickel, nichrome, hafnium, niobium, zirconium,vanadium or tungsten.
 12. The damascene structure of claim 10, whereinthe conductive ceramic is tantalum nitride, indium oxide, coppersilicide, tungsten nitride or titanium nitride.
 13. The damascenestructure of claim 1, wherein the seed layer is made of Cu, Co, Al, Agor a combination thereof.
 14. The damascene structure of claim 1,further comprising a metal layer disposed on the seed layer.
 15. Thedamascene structure of claim 14, wherein the metal layer is filled inthe damascene opening.
 16. The damascene structure of claim 14, themetal layer is made of copper.
 17. A damascene structure, comprising: adielectric layer disposed on a substrate and having a damasceneinterconnect; a barrier layer disposed on an inner surface of thedamascene interconnect and comprising two portions separated by a defectexposing the dielectric layer; a repair layer comprising: a metalportion laminated on the two portions of the barrier layer; and aninsulating metal oxide portion filled in the defect to cover thedielectric layer exposed by the defect; and a seed layer conformallydisposed on the repair layer.
 18. The damascene structure of claim 17,further comprising a metal interconnect disposed on the seed layer andin the damascene interconnect.
 19. A damascene structure, comprising: adielectric layer disposed on a substrate, wherein the dielectric layerhas a damascene opening; a barrier layer disposed on an inner surface ofthe damascene opening; a repair layer disposed on the barrier layer,wherein the repair layer disposed on the barrier layer is composed of ametal, and the repair layer disposed on the dielectric layer exposed bydefects in the barrier layer is composed of insulating metal oxide; aseed layer conformally disposed on the repair layer; and a metalinterconnect disposed in the damascene opening.
 20. The damascenestructure of claim 19, wherein the metal of the repair layer is Al, Ru,Co, Mn, or Ta.